1. Field of the Invention
The present invention relates to an image reading device that is included in a copying machine or the like and reads images of original documents, as well as to an image forming apparatus having such device, and more particularly to an image reading device that also functions as an operation panel and to an image forming apparatus having such device.
2. Description of the Prior Art
An image forming apparatus such as a copying machine, for example, conventionally includes an image reading device that reads images of original documents. An image reading device generally includes a platen glass on which the original document is placed, a photoelectric conversion element or the like that receives the light emitted to the original document surface via the platen glass and reflected therefrom and converts this light into electric signals. In addition, an image forming apparatus includes an operation panel, and the user of the apparatus inputs various desired operation parameters via this operation panel. For example, in a copying operation carried out using a copying machine, copied images are formed based on the image data read by the image reading device and in accordance with the input copying operation parameters.
Such an operation panel is often disposed on the front side or top side of the apparatus to enable easy use thereof by the user. Furthermore, because the operation panel must be made compact due to space limitations, while the number of display items has increased with the increasing number of functions incorporated in image forming apparatuses in recent years, a layered system or the like is often used for the display. However, it is still sometimes difficult to determine the relationship between the original document size and the actual print size, or the setting of printing orientation. In view of this problem, Japanese Laid-Open Patent Applications H5-40317 and H7-84233 disclose copying machines having a platen glass comprising a photo-transmitting liquid crystal panel. According these technologies, information such as the position and size of the original document can be displayed on the liquid crystal panel in a way that is easy to understand.
However, because a liquid crystal panel is used in both of the conventional technologies mentioned above, the viewing angle is narrow, and depending on the position or the height of the user, the display may be difficult to see. In addition, the problem exists that because liquid crystal is not a self-illuminating display, it requires light, which leads to a complex apparatus construction. Furthermore, because a liquid crystal panel generally uses a deflecting plate and the panel thickness is in the order of several millimeters due to the considerable thickness of the liquid crystal cells, the amount of light declines significantly when light is transmitted through the panel. As a result, in an image reading device that illuminates an original document from below the platen glass using a lamp or the like and inputs the reflected light to a photoelectric conversion element, noise may increase and lead to a deterioration in image quality.
Furthermore, with an apparatus in which instructions are input via the operation panel while the user views the display thereon, as in the case of the technology disclosed in the Japanese Laid-Open Patent Application H7-84233 mentioned above, while detailed instructions can be provided, the buttons and the like used for input purposes tend to become small, which may render the apparatus less easy to use. Moreover, if letters or the like are to be added to the printing, it is difficult to accurately input such letters in the desired positions, resulting in a number of input attempts while viewing the display.